NASHVILLE, Tenn. (AP) — Former Tennessee Democratic Gov. Phil Bredesen and Republican U.S. Rep. Marsha Blackburn have been running their campaigns for a critical U.S. Senate seat like their matchup was assured.

Voters made it official Thursday.

Bredesen and Blackburn disposed of minimal opposition in their primary elections, kicking off what’s expected to a bruising, expensive fight that could determine Democrats’ chances of overturning the 51-49 Republican Senate majority.

Polls have indicated a close contest to replace retiring Republican Sen. Bob Corker.

A general election win would be historic for Blackburn, who would become the first female U.S. senator ever elected in Tennessee.

Voters faced a more competitive field in the race for the nomination to replace term-limited Republican Gov. Bill Haslam.

Former Nashville Mayor Karl Dean won the Democratic primary, defeating state House Minority Leader Craig Fitzhugh after outspending him $4.4 million to $984,800.

Taking a page from Bredesen’s playbook, Dean has touted himself as a leader who can break down partisan barriers and make divided government work during divisive political times. He told his supporters Thursday he intended to run a positive race focused on jobs, affordable health care and good education.

Daniel Tashian.

Businessman Bill Lee won a bruising GOP primary. He mostly stayed out of the fray while other opponents savaged each other in attack ads. Lee billed himself as the race’s only conservative outsider and emphasized his Christian faith. “I am someone who is not a politician, but I do have a vision for Tennessee to lead the nation,” Lee told supporters during his victory speech.

The field also included U.S. Rep. Diane Black, who began the campaign as the favorite and got the endorsement of Vice President Mike Pence but stumbled to a third-place finish.

No Democrat has won statewide here since Bredesen was re-elected governor in 2006, when he clinched all 95 counties. It’s been an even longer drought in the Senate, with the last Democratic victor former Vice President Al Gore in 1990.

Bredesen, who remains popular, would again need to peel off support from moderate Republicans and independents. He is pledging to work across party lines, saying he will support Trump on policies that are good for the state, and oppose him when they aren’t.

He thanked his supporters Thursday night and vowed to be “the best damn senator you ever sent up to Washington.”

Blackburn is a strong Trump backer in a state that voted for the president by 26 percentage points in 2016. She has run in support of Trump’s agenda, including his wall-building immigration crackdown and his U.S. Supreme Court pick, Brett Kavanaugh.

“We know what Tennesseans say that they want to see in their next senator is somebody who is going to stand with President Trump to finish the agenda that they voted for when they elected him and sent him to Washington,” she told her supporters, some of whom were wearing T-shirts emblazoned “Marsha Marsha Marsha.”

Blackburn has billed herself as a “hardcore, card-carrying Tennessee conservative” from the outset of her campaign. She has benefited from center-stage appearances alongside Trump and Pence in public events and fundraisers in Tennessee.

Pence and Trump have already attacked Bredesen, saying he’s too liberal for Tennessee and would fall in line with Democratic Minority Leader Chuck Schumer.

Bredesen has countered that his record as governor shows he’s an independent thinker who won’t cave to party leaders.

Bredesen has criticized Trump’s tariff policies, which threaten an estimated $1.4 billion in Tennessee exports, according to the U.S. Chamber of Commerce, a longtime Republican ally. The exports are linked to more than 850,000 jobs in the state related to farming, steel, baked goods, car manufacturing, whiskey distillers like Jack Daniel’s, and more, the chamber said.

Blackburn has expressed “grave concern” about the tariffs, but said she appreciates the administration’s goal of punishing bad actors like China. She asked the commerce secretary to reconsider broad tariffs to avoid harm to Tennessee’s economy.

Blackburn has opposed Corker’s proposal to require a congressional vote on tariffs issued in the name of national security, a move that fellow Tennessee GOP Sen. Lamar Alexander supports.

Tennessee has a history of electing centrist senators. Corker, for one, has further complicated the race by saying he’s supporting Blackburn but won’t actively campaign against Bredesen, whom he has called a friend.

Corker also has very publicly tussled with Trump, once saying he had turned the White House into an “adult day care center,” with the president tweeting in response that Corker “couldn’t get elected dog catcher in Tennessee.” Corker endured booing at a Trump-Blackburn rally in Nashville this spring.

Heading into July, Blackburn maintained an early 2-to-1 cash advantage over Bredesen, with $7.3 million in her bank account. But Bredesen would be one of the wealthiest members of Congress if elected and has already loaned $3.5 million of his own money to his campaign.